The USB-A port on the device acts like a USB-A port directly attached to your computer, so yes, you can plug thumb drives into it.... ASSUMING the drive isn't so wide that it obstructs the HDMI port, which you might simultaneously need.

I have such an adapter that I have bought a couple of years ago. When I try to watch a 4K movie I have rented on iTunes connecting my iPad Pro 11inch with the adapter I already have I receive the following message "This adapter doesn't support HDR. Try to stream the movie instead. YES - NO".
Is this a newer version of this adapter supporting HDR or not?
Will I be able to connect my iPad with this adapter and watch 4K HDR movies without the streaming it?

I used the lithgning to USB 3 camera adapter to connect audio interfaces/midi devices such Yamaha keyboards to the iPad Pro 9.7”. I would like to change to the new iPad Pro 11” and still be able to keep using my music apps with the keyboard

I have recently buy a MacBook 12" and this multiport, because I will use it for my classes in the university.
Most of the projectors are VGA, so I bought a HDMI-VGA adapter as well.
I have tested it with 2 different projectors and the MacBook did not recognized them.
Then, I get from a collegue a generic USB-C/HDMI adapter, and the projector was recognized.
The tests I have performed are:

The USB-C Digital AV Multiport Adapter can only deliver 60W so the 15" MacBook Pro will NOT charge AT ALL if it is also being used heavily. I had this problem. Finally I found support doc HT207256: "MacBook Pro can receive a maximum of 60W of power through the Apple USB-C VGA Multiport Adapter or USB-C Digital AV Multiport Adapter. For the best charging performance on MacBook Pro (15-inch, 2016), connect the power supply directly to your Mac."

No. I have been talking to several people with Apple, and currently, there is no solution that allows the use of your thunderbolt display with the new macbook with USB-C. I hope they will make a usb-c to thunderbolt adaptor, but there is some indication that the new macbook may not even have the electronics to drive the thunderbolt interface.

I have used this adaptor with my 2016 MacBook and successfully run a WD Essential USB disk with it. The drive draws all its power from the adapter. I initially used it with the adaptor plugged into the wall socket for power and the disk operated fine. When I unplugged the USB-C lead supplying power to the adapter the HD ungracefully ejected itself and powered down. I unplugged the drive and plugged it back in again with no power connected and it worked fine. So, in summary, this adapter supports a WD Essential drive that draws power from it and will operate with or without power, but I would avoid either plugging, or unplugging the adapter with a disk mounted to it. I only tested it with a WD Essential, other disks may draw more power and not work with this adapter.

Since HDMI Alt Mode requires three of the four USB-C Super Speed+ lanes, there are not enough lanes for USB 3.0 (two lanes: one for receive, and one for transmit), therefore this adapter only supports High Speed USB (USB 2.0). It's sad that Apple doesn't mention what speed of USB is supported by this adapter.

There are adapters that can convert HDMI 1.4 to DisplayPort 1.2 but HDMI 1.4 only allows 4K at 30 Hz. I'm not sure if the LG UltraFine 4K supports 4K at 30 Hz. Those adapters require a USB connection for extra power, but the Apple TV doesn't have any USB ports, so you'll need another USB source.

There might be new adapters coming later in 2018 that can convert HDMI 2.0 to DisplayPort 1.2.

Then you can add a DisplayPort to USB-C cable to connect the adapter to the LG UltraFine 4K. However, the DisplayPort connection does not include USB, so any USB functions of the Display will not work (speakers, brightness control, USB ports). The display only supports USB 2.0, because all four USB-C Super Speed+ lanes are required for 4K at 60 Hz. Even if DisplayPort could pass USB (using the AUX lines), the HDMI 1.4 to DisplayPort 1.2 adapter would not include USB.

The LG UltraFine 5K display can support 5K at 60 Hz and USB 3.0 because Thunderbolt uses the USB-C cable's lanes at twice the speed of USB 3.1 gen 2. However, the LK UltraFine 5K display requires a Thunderbolt 3 connection.